White "smoke" is raw, unburned, atomized diesel fuel. Steam is often mistaken for white smoke and, as irishwoodsman points out, would indicate coolant entering the combustion chamber. You will need to determine which it is, fuel or steam, before considering what action to take.
You can usually discern the distinct smell of the fuel. Or, try holding a piece of printer paper in the exhaust stream and if the substance is fuel it will soak the paper and not evaporate whereas steam will soak the paper and then it will dry out.
Your painting efforts may not be related to the problem as it could have happened coincidentally to a failure of some sort. Although, if you have an aftercooler and you were not careful to keep dirt and debris from falling into the blower area when you removed the turbo, something could have holed the heat exchanger under the blower.